An optical disc is a generic nomenclature of disc-shaped storage media in which data are read/written using laser light. Among optical discs, presently, although CDs, DVDs, or the like are generally used, next-generation discs such as Blue-ray Discs (hereinafter referred to as “BD” for the simplicity sake) or HD-DVDs have begun to appear on the market. These optical discs are used as not only a data medium for storing data of computers but also as a medium allowing recording and reproduction of music videos in exclusive devices. An optical disc drive is a storage unit that rotates an optical disc to read/write data from/to the optical disc. In personal computers (hereinafter, simply referred to as “PC”), regardless of their type such as a desktop or a notebook, optical disc drives are mounted on most of the products.
Optical discs are similar in their external appearance but are manufactured according to various different standards and thus often cause user confusion when using them. With regard to data medium alone, CDs, DVDs, BDs and HD-DVDs can be classified into various categories: read-only ones; once-writable ones; plural-times-rewritable ones; and so forth. To meet these many standards, there exist many types of optical disc drives. As typical types of optical disc drive, there are a CD-ROM drive in which data can only be read from CDs, a DVD-ROM drive in which data can be read from CDs and DVDs, a combo drive in which data can be read from CDs and DVDs but cannot be written to DVDs, and a super-multi drive in which data can be read/written from/to CDs and DVDs. Particularly, optical disc drives such as the combo drive and the super-multi drive, in which data writing is possible, are becoming popular in recent years. Included next-generation standards such as BD or HD-DVD in the above-mentioned ones, the number of types of the optical disc drives will much more increase.
Now, known technologies for allowing read-only access from a computer to a storage unit in which data can be read/written will be described. According to a technology taught in Japanese Laid-open (Kokai) Patent Publication No. 2006-309296, a BIOS confirms settings on permission/non-permission to use a storage unit, which is set by a supervisor, during startup of a computer, and based on the permission settings confirmed, initialization of the storage unit is inhibited, thereby restricting the use thereof. Also taught is a technology for restricting writing of data to the storage unit by using a filter driver during a control by an operating system (hereinafter, simply referred to as “OS”). According to a technology taught in Japanese Laid-open (Kokai) Patent Publication No. 2004-047041, a write protection unit is provided between a computer and a magnetic disc drive to set the magnetic disc drive to a write inhibit mode. According to a technology taught in Japanese Laid-open (Kokai) Patent Publication No. 2002-251324, a disc drive switches its mode by a switch operation between a writable mode and a non-writable mode. According to a technology taught in Japanese Laid-open (Kokai) Patent Publication No. 2007-012123, by forcibly erasing a portion of flash memory areas by a process of firmware, a write function of an optical disc drive is invalidated so that the optical disc drive is used only for reading.
As described above, with the popularization of optical disc drives in which data can be read/written (such feature hereinafter referred to as “rewritable”), manufacturers of the optical disc drives are stopping manufacturing of read-only optical disc drives, in which only date reading is possible, in order to cut down the number of components or products and to thus get the cost down. For this reason, only the rewritable optical disc drives are put into the market and thus it has become difficult to buy a read-only optical disc drive.
Further, to meet the various optical disc standards described above, there are many types of optical disc drives. Whenever a new optical disc standard is developed, the types of the optical disc drives will increase much more. Therefore, the PC makers need to decrease the number of types of components stored for manufacture and maintenance as much as possible to make component management easy or get the cost down. For this reason, many PC makers are not holding such read-only optical disc drives as components.
However, it cannot be said that such read-only optical disc drives have become completely unnecessary. For example, corporate or public authority users are reinforcing their security management to prevent illegal leaks of massive personal or confidential information handled in their businesses. As an example of the route of the information leaks, a user may remove a recording medium, in which data are written using a rewritable storage unit, from a PC and take the medium to the outside. To prevent this, the corporate or public authority users may sometimes need to order special PCs for business use in which storage units, such as an optical disc drive, in which a recording medium is removable from the PCs solely or along with a storage unit, are configured for read-only use. The PC makers therefore need to make PCs having a read-only storage unit mounted therein in order to meet such needs.
To cope with such problems, a method can be considered in which a rewritable optical disc drive is incorporated in a PC and configured for read-only use before shipping the PC. According to the technology of Japanese Laid-open (Kokai) Patent Publication No. 2006-309296, under the control of OS, a device driver restricts sending a write command from a PC to a rewritable optical disc drive which cannot be set for a read-only mode, whereby the optical disc drive is substantially treated as being configured for read-only use. However, among application software operated by an OS such as WINDOWS (registered trademark), some software can perform direct data access to an optical disc drive without a device driver that the OS provides to the application software. In such a case, even when the technology of Japanese Laid-open (Kokai) Patent Publication No. 2006-309296 is employed, there is a risk that a write command is directly sent from the application software to the optical disc drive without intervention of the device driver.
In addition, by using FLOPPY (registered trademark) discs, CD-ROMs, externally attached hard disk drives (hereinafter, simply referred to as “HDD”), and the like, a user can install and load another OS different from the OS normally installed in a built-in HDD of a PC. However, when the technology of Japanese Laid-open (Kokai) Patent Publication No. 2006-309296 is employed, a user can start up a device driver included in another OS, different from the device driver configured to prevent sending of a write command; therefore, the sending of a write command is not restricted.
Meanwhile, an optical disc drive according to the technology of Japanese Laid-open (Kokai) Patent Publication No. 2007-012123 forcibly interrupts a write function of an originally rewritable optical disc drive and sets the optical disc drive to operate in a read-only mode. When such an optical disc drive is mounted in a PC, usually, an OS sends a command to the optical disc drive to set it to a read-only mode and the optical disc drive executes the command to operate in the read-only mode. However, even in such a case, there is a possibility that a command for canceling or changing the read-only mode can be sent from application software capable of direct data access to the optical disc drive without intervention of a device driver. Also, a case can be assumed such that another unexpected OS is installed and put into operation to prevent a command for setting a read-only mode in an optical disc drive from being sent to the optical disc drive or to send a command for canceling or changing the read-only mode to the optical disc drive, whereby a successful read-only mode operation is not ensured.
In addition, when a user removes an optical disc drive that can be set to a read-only mode from a PC in which the optical disc drive was originally mounted and attaches to the PC a rewritable optical disc drive that cannot be set for the read-only mode, the optical disc drive will not execute the command from an OS for setting the optical disc drive for the read-only mode, whereby a successful read-only mode operation is not ensured. Particularly, most of today's PCs have a swappable bay that allows attachment, removal, or replacement of peripheral devices such as an optical disc drive in a state where a PC is powered on and an OS is operating. When an optical disc drive is removably connected to a PC by the swappable bay, since it is easy to replace the optical disc drive, there is a high risk that a rewritable optical disc drive that cannot be set to a read-only mode is attached to the PC in a state where the optical disc drive can operate.
As discussed above, according to the method known in the art, it is practically impossible to ensure security even when one tries to operate a rewritable optical disc drive in a read-only mode. From the perspective of preventing information leaks, a method can be considered in which attachment of another optical disc drive to a PC is inhibited or an interface used to connect an optical disc drive to a PC is disabled. However, such a method would inhibit installation of verified application software used in business or even inspection of data and as a result, would harm the convenience of users. The same problem can occur, without limiting to the optical disc drives, in most rewritable storage units such as a hard disc drive or a semiconductor storage unit, which can be removably attached to or incorporated in PCs.
A need has arisen, therefore, to provide a method for securely permitting a computer to set security to a storage unit from/to which data can be read/written. There is also a need to provide a computer capable of performing such a security setting. There is further a need to provide a computer program (BIOS) product that permits a computer to perform such setting.